Boiler AIR AND FLUE GAS SYSTEM
 

[LEFT][B][I][U][F**T=&quot]Boiler AIR AND FLUE GAS SYSTEM[/F**T][/U][/I][/B]
[B][I]
"We talked before about [/I][/B][B][I][COLOR=black][F**T=Arial]HITACHI [/F**T][/COLOR][/I][/B][B][I]Boiler Overview (Steam Generator), we menti**ed the characteristics of the boiler, Parameters of operating Steam and water.[/I][/B]
[B][I]At this article we will make a focus ** air and flue gas system at boiler."[/I][/B]
[B] -The boiler air and flue gas system c**sists of [U]combusti** air system[/U], [U]gas recirculati** system[/U] and [U]flue gas system[/U]. [/B]
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[F**T=Impact]1) Combusti** air system[/F**T]
[B]-The combusti** air system c**sists of two forced draft fans, two steam coil air heaters and two air heaters. Two 60% capacity centrifugal forced draft fans are provided to supply the combusti** air to the windbox and after air port with adequate flow rate and pressure for combusti**. The forced draft fan draws air from the atmosphere through the inlet silencer, and discharges air to the steam coil air heater, the air heater and the windbox. Modulating inlet vane of the centrifugal forced draft fan c**trols the combusti** air flowing to the boiler wind box and after air port. Air heater inlet air damper creates the suitable backpressure for seal air supply through the forced draft fan outlet c**necting air duct. [/B]
[B]-Combusti** air flow is measured by flow element located at the outlet of air heater. Two 50% capacity, bi-sector, vertical shaft regenerative type air heaters are provided to heat combusti** air using flue gas from the ec**omizer. To achieve in-furnace NOx reducti**, two-stage combusti** system using the after air port dampers is applied. Part of the combusti** air is supplied to the after air ports for two-stage combusti**. The after air port damper (4 dampers) c**trol shall be modulated to maintain the optimum two-stage combusti** at each load.[/B]

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[F**T=Impact]2) Gas Recirculati** system[/F**T]
[B][COLOR=black]-The gas recirculati** system c**sists of two gas recirculati** fans. Two 60% capacity centrifugal gas recirculati** fans are provided to supply gas recirculati** flow to the furnace for reheat steam temperature c**trol. The gas recirculati** fan draws flue gas from the ec**omizer outlet flue gas duct and discharge gas to the furnace. Modulating inlet damper c**trols gas recirculati** flow rate. The gas recirculati** flow set point is derived from the reheat steam temperature c**trol.[/COLOR][/B]

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[F**T=Impact]3) Flue Gas system[/F**T]
[B][COLOR=black]-The flue gas system c**sists of two air heaters. The combusti** gas transfers its own heat to the water wall, the superheaters, the reheater and the ec**omizer, then leaves the boiler to the flue gas ducts. The flue gas goes to the stack through the AH and is exhausted to the atmosphere[/COLOR][/B].


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[F**T=Impact]*** Steam Coil Air Heater[/F**T]
[B][COLOR=black]-Two 50% capacity steam coil air heaters are installed in the combusti** air duct upstream of the air heaters to heat combusti** air before air flows into the air heaters. The steam coil air heater raises the air heater cold end temperature to predetermined set point over the entire load range when fuel (Mazout) oil is burnt. The steam coil air heater is a finned, steel tube heat exchanger. Steam Used for heating flows through the tube side, Combusti** air is heated as it flows across the outside of the finned tubes. [/COLOR][/B]
[B][COLOR=black]-Steam coil air heaters are installed vertically at the air heater inlet duct. The steam coil air heater casing and coil secti** covers the full dimensi** of the duct. Heating steam is supplied for the steam coil air heater system from auxiliary steam system.[/COLOR][/B]

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[B][COLOR=black] [/COLOR][/B]
[B][COLOR=black] [/COLOR][/B]
[B] [/B][B][F**T=&quot]“This descripti** is about HITACHI Steam Generator “[/F**T][/B][F**T=&quot][/F**T]
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